Charging battery bank via solar and alternator simultaneously?

DLTooley

Observer
I **think** what you want to do is connect the alternator on the other side of the controller. With Flooded Lead Acid the regulator will act as the controller. Theoretically! There will be voltage drop presuming the run from the alternator to the house battery is of some distance. That puts the margin of error in the right direction. For a number of reasons the alternator is best for bulk and absorption phases.
 
Have a similar concern hoping someone can add info.

I have a charge controller connected to my battery and panels on that. All is great shuts power off from the panels when charged and connects power from the panels when needed. To this i want to add an Alt. feed to supplement the solar when it either isn't putting out or cant put out. Im not worried about the battery or anything "behind" the controller but in regard to the panels themselves.

Will it be safe for the solar panels so see this feed from the Alt. or will a power supply on the panels some how "blow" them out (basically running the Alt and Solar in parallel into the controller)? Im assuming that it should be fine since if panels are wired together and some get sun but other dont, some would "see" voltage from the others and they are fine, but anyone know for sure?

Diagram of how I want to hook this up is attached.

TIA for any help

Dont do it !
Alternator can output far more current than most charge controllers are capable of carrying.

If your solar is same voltage and its battery is of similar chemistry as the car, just connect alternator to solar battery thru a isolating relay of your favourite type.

So I wanted to follow up on this. I did this but with a DPDT switch between the truck and the solar panels so I could manually switch between the 2 sources going into the charge controller. And it works. Not sure why everyone (I posed this question in other places too) kept saying not to try this without really any supported reasoning why but I did it anyway (the main risk was a $30 charge controller and that was acceptable to me).

My OEM trailer wiring will apparently support up to 30A at least that's what the factory fuse is rated to. I have a 20A solar controller...important thing to note here is that, at least in my case, the Amp rating on the charge controller is BOTH the max charge current and max output current capability so make sure you have headroom. I bought mine based on the max output and was unaware of what the max charging could be. So I was very surprised to see that my "house" battery when charging off the truck will charge at a rate up to 20A (though it typically only maintains about 17A continuous). This frightened me at first because most battery chargers have like a 6A and 2A charge setting and this seems really high in comparison but given that batteries can purportedly handle charge current at about 20%-25% of their rated AH rating and this is a 95AH battery I should be good. Additionally this rate is not always constant, the charge controller does do it's thing and as the battery charges has been dropping Amps and is now typically charging at roughly 10A after a few 1hr commutes home from work.

An interesting note in my case is that the charge controller also seems to have some logic built in (based on resistance maybe???) and it seems will only pull a "safe" amount of amperage to charge based on the wire gauge used??? As an example when I hooked everything up to test I had really small gauge wire, like 20awg as I just wanted to see what would happen. I noticed that the controller was charging the battery at a max of about 8A. Max I saw on solar charging was like 5A so that seemed about right. So I ran the connections with 16awg wire so it would be plenty capable. But with the 16awg wire the controller will typically charge at a constant 17A when the battery is low, tapering off as the battery charges. None of this is mentioned in the "extra" good chineese instructions, lol ;) Anyone know more about how that's accomplished?
 
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The Goat

New member
Have a similar concern hoping someone can add info.

I have a charge controller connected to my battery and panels on that. All is great shuts power off from the panels when charged and connects power from the panels when needed. To this i want to add an Alt. feed to supplement the solar when it either isn't putting out or cant put out. Im not worried about the battery or anything "behind" the controller but in regard to the panels themselves.

Will it be safe for the solar panels so see this feed from the Alt. or will a power supply on the panels some how "blow" them out (basically running the Alt and Solar in parallel into the controller)? Im assuming that it should be fine since if panels are wired together and some get sun but other dont, some would "see" voltage from the others and they are fine, but anyone know for sure?

Diagram of how I want to hook this up is attached.

TIA for any help

Very interested in this, as i am wanting to do a very similar thing in my setup. Except i will have fused DC charge (240w 20amp) from the truck battery, not direct from the alternator, and want to use an MC4 2-to-1 cable to combine input from a 100w Renogy Eclipse panel with the DC input from the truck battery. All input is going to a in built 30amp rated charge controller in my Inergy Kodiak. Would love to know if there's any risk in this. The way i see it: Kodiak input rated 600w or 30amp max, so 240w truck DC + 75w (nominal) solar = 315w @12v = 26.25 amp = safe-input.

But i am very new to solar/DC and may be completely over simplifying.
 
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Very interested in this, as i am wanting to do a very similar thing in my setup. Except i will have fused DC charge (240w 20amp) from the truck battery, not direct from the alternator, and want to use an MC4 2-to-1 cable to combine input from a 100w Renogy Eclipse panel with the DC input from the truck battery. All input is going to a in built 30amp rated charge controller in my Inergy Kodiak. Would love to know if there's any risk in this. The way i see it: Kodiak input rated 600w or 30amp max, so 240w truck DC + 75w (nominal) solar = 315w @12v = 26.25 amp = safe-input.

But i am very new to solar/DC and may be completely over simplifying.

I dont think that will work.
1. Your truck battery will not power the charge controller enough to charge another battery because you need higher voltage to charge a second battery, the truck battery voltage will not be high enough to really ever top off a second battery.
2. Combining the solar panel input and truck battery input going into the charge controller will effectively just have a the solar constantly charging the truck battery and the charge controller will be doing nothing to regulate that. It will only top up the "house" battery when the solar kicks in to override the incoming truck battery voltage into the controller and then since the panel will be also supplying that same voltage to the truck battery without any regulation it will be trying to charge both sources.

You need to be able to switch between power sources, solar OR(not AND) truck (alternator, not battery) to charge a second battery.
 
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john61ct

Adventurer
Have a similar concern hoping someone can add info.

I have a charge controller connected to my battery and panels on that. All is great shuts power off from the panels when charged and connects power from the panels when needed. To this i want to add an Alt. feed to supplement the solar when it either isn't putting out or cant put out. Im not worried about the battery or anything "behind" the controller but in regard to the panels themselves.

Will it be safe for the solar panels so see this feed from the Alt. or will a power supply on the panels some how "blow" them out (basically running the Alt and Solar in parallel into the controller)? Im assuming that it should be fine since if panels are wired together and some get sun but other dont, some would "see" voltage from the others and they are fine, but anyone know for sure?

Diagram of how I want to hook this up is attached.

TIA for any help

Very interested in this, as i am wanting to do a very similar thing in my setup. Except i will have fused DC charge (240w 20amp) from the truck battery, not direct from the alternator, and want to use an MC4 2-to-1 cable to combine input from a 100w Renogy Eclipse panel with the DC input from the truck battery. All input is going to a in built 30amp rated charge controller in my Inergy Kodiak. Would love to know if there's any risk in this. The way i see it: Kodiak input rated 600w or 30amp max, so 240w truck DC + 75w (nominal) solar = 315w @12v = 26.25 amp = safe-input.

But i am very new to solar/DC and may be completely over simplifying.
Start your own thread, and specify

A. what your electrical needs and usage patterns are, driving patterns, access to mains, weather etc

B. and exactly what equipment you already have as well as what you're proposing using.

Ideally with links to their technical specs.
 

dwh

Tail-End Charlie
??? well that answer helped the archival of information lol.... IF anyone has an idea on where/what the other thread is would certainly appreciate a link.

bjayf, who I was replying to, had another thread going at the same time. Go back to my post that you quoted, look just above that to bjayf's post that I quoted.

Click his handle. After the little drop down shows up with his stats, click his name again. Then click on his posts and that other thread will show up.

At least, that's how I found it...since I'd forgotten all about it.
 

dwh

Tail-End Charlie
I dont think that will work.
1. Your truck battery will not power the charge controller enough to charge another battery because you need higher voltage to charge a second battery, the truck battery voltage will not be high enough to really ever top off a second battery.
2. Combining the solar panel input and truck battery input going into the charge controller will effectively just have a the solar constantly charging the truck battery and the charge controller will be doing nothing to regulate that. It will only top up the "house" battery when the solar kicks in to override the incoming truck battery voltage into the controller and then since the panel will be also supplying that same voltage to the truck battery without any regulation it will be trying to charge both sources.

You need to be able to switch between power sources, solar OR(not AND) truck (alternator, not battery) to charge a second battery.

Not to mention that hooking the engine battery and the solar together without a charge controller in between will allow the solar to potentially drive the engine battery's voltage all the way up to the solar's Vmp.

It would probably never actually get all the way up to Vmp, buy it could still overcharge the engine battery. A lot.

The primary purpose of any charge controller is to protect a battery from overcharge.
 

Coachgeo

Explorer
bjayf, who I was replying to, had another thread going at the same time. Go back to my post that you quoted, look just above that to bjayf's post that I quoted.

Click his handle. After the little drop down shows up with his stats, click his name again. Then click on his posts and that other thread will show up.

At least, that's how I found it...since I'd forgotten all about it.
Found it. Luckly (but the again.... rather everyone be more active) .... he had only started two threads... this one and the one other. If it had been someone like yourself.... combing thru all their started threads would take forever to find the right one.

Anyway...... if anyone is curious..... Here is the link.. https://www.expeditionportal.com/fo...ies-and-a-noco-genius-onboard-charger.149310/ and on page two is "the answer" offered about this topic
 

wb9wb

Member
Question. The blue sea ACR is rated at 120 amps, and my Jeep JK has a 160 amp alternator. Best way to deal with it? Get something else? 100 amp fuse? etc?

thanks
 

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